Abstract:
The dairy industry is a vital constituent in livestock which is a substantial part of
agriculture and significantly contributes to the local economy producing approximately
42 million litres of milk per month. Indiscriminate use of antibiotics in livestock industry
is considered to be a reason for emerging antibiotic resistance among dairy
bacteria. Investigating the antibiotic resistance of such bacteria is essential to prevent
adverse effects on animal and public health through corrective measures. The current
study aimed at isolation and identification of dairy faecal bacteria and determine their
antibiotic resistance. Freshly voided faecal samples were collected from ten cattle at
a dairy farm in Kandy, Central Province, Sri Lanka in March 2022. Faecal bacteria
were isolated by standard microbiological techniques. Morphological and biochemical
tests were performed on 35 chosen bacterial colonies for identification. Kirby-Bauer
disk diffusion method (CLSI) was employed on 6 representative bacterial spp to detect
susceptibility for 10 antibiotics. In this study, 6 bacterial species identified were Bacillus
spp (62.9%), Staphylococcus spp (11.4%), Pseudomonas aeruginosa (8.6%), Enterobacter
spp (8.6%), Escherichia coli (5.7%), and Streptococcus spp (2.9%). All six tested isolates
were sensitive to Amikacin, Chloramphenicol, Enrofloxacin, Gentamycin, and Imipenem.
Five isolates were sensitive to Ciprofloxacin, Streptococcus spp indicating intermediate
susceptibility. The highest resistance was shown against Ampicillin (66.6%) followed by
Amoxicillin (50%). S. aureus was resistant to Amoxicillin, Ampicillin and Cefuroxime.
B. subtilis, Streptococcus spp, and E. coli each were resistant to two antibiotics. The
effect of Tetracycline was intermediate on S. aureus and Enterobacter spp while other
bacteria were susceptible. Present results revealed the complete susceptibility of examined
bacteria to five antibiotics critically or highly important to animals and humans,
suggesting low selection pressure. However, higher resistance to two Aminopenicillins
and reduced effectiveness of other three antibiotics indicate the need to minimize resistance
development in the farm through modified management practices.
